1. Field of the Invention
This invention relates to burglar alarms. More particularly, it relates to a non-electrical bell adapted to be affixed to a door in such a manner that it sounds when the door is opened.
2. Description of the Prior Art
U.S. Pat. No. 713,780 of MacDonald shows a door burglar alarm operated by a weight attached by means of a hook to a bar which fits between the door and the door jamb. When the door is opened the weight falls on a cap which explodes when hit by the weight. Bell, U.S. Pat. No. 1,483,708 teaches use of a ball fitting around a post which moves from one end of the post to the other when the post is turned over to give visual notice of a fare-box in which it is contained having been tampered with. Mohler, in U.S. Pat. No. 1,003,636 discloses a rod surrounded along part of its length by a spring, the rod having a hammer adapted to strike a bell when a refrigerator pan overflows. None of the foregoing teaches how to simply and efficiently sound an alarm when someone breaks into a house without danger to someone who might be at or near a door as it is broken through.